Context Free Grammar is formal grammar, the syntax or structure of a formal language can be described using context-free grammar (CFG), a type of formal grammar. The grammar has four tuples: (V,T,P,S).

V - It is the collection of variables or nonterminal symbols.
T - It is a set of terminals. 
P - It is the production rules that consist of both terminals and nonterminals.
S - It is the Starting symbol.